• 1.3 baseline — 0.6 × season 1.1 (14 gm) + 0.4 × last 10 1.6
• −0.4 opponent leak — they concede 16.2/game vs a 23.7 league average
• +0.2 at this ground — averages 1.5 there (35 gm)
• vs them: averages 5.3 over 3 games — evidence, never summed

Derived, not measured — plain arithmetic over his real games, shown in full. Adjustments can overlap (a game at this ground can also be a wet one); they add simply, and this note is the admission.